@article{tsai_pillai_ganeshan_saeed_gao_duin_augustyn_balke_2023, title={Effect of Electrode/Electrolyte Coupling on Birnessite (delta-MnO2) Mechanical Response and Degradation}, volume={15}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.3c02055}, DOI={10.1021/acsami.3c02055}, abstractNote={Understanding the deformation of energy storage electrodes at a local scale and its correlation to electrochemical performance is crucial for designing effective electrode architectures. In this work, the effect of electrolyte cation and electrode morphology on birnessite (δ-MnO2) deformation during charge storage in aqueous electrolytes was investigated using a mechanical cyclic voltammetry approach via operando atomic force microscopy (AFM) and molecular dynamics (MD) simulation. In both K2SO4 and Li2SO4 electrolytes, the δ-MnO2 host electrode underwent expansion during cation intercalation, but with different potential dependencies. When intercalating Li+, the δ-MnO2 electrode presents a nonlinear correlation between electrode deformation and electrode height, which is morphologically dependent. These results suggest that the stronger cation-birnessite interaction is the reason for higher local stress heterogeneity when cycling in Li2SO4 electrolyte, which might be the origin of the pronounced electrode degradation in this electrolyte.}, number={21}, journal={ACS APPLIED MATERIALS & INTERFACES}, author={Tsai, Wan-Yu and Pillai, Shelby B. B. and Ganeshan, Karthik and Saeed, Saeed and Gao, Yawei and Duin, Adri C. T. and Augustyn, Veronica and Balke, Nina}, year={2023}, month={May}, pages={26120–26127} }
 @article{pillai_wilcox_hillis_losey_martin_2022, title={Understanding the Water-in-Salt to Salt-in-Water Characteristics across the Zinc Chloride : Water Phase Diagram}, volume={126}, ISSN={["1520-5207"]}, url={https://doi.org/10.1021/acs.jpcb.1c10530}, DOI={10.1021/acs.jpcb.1c10530}, abstractNote={Using a series of time- and temperature-resolved synchrotron diffraction experiments, the relationship between multiple polymorphs of ZnCl2 and its respective hydrates is established. The δ-phase is found to be the pure anhydrous phase, while the α, β, and γ phases result from partial hydration. Diffraction, gravimetric, and calorimetric measurements across the entire ZnCl2·R H2O, 0 > R > ∞ composition range using ultrapure, doubly sublimed ZnCl2 establish the ZnCl2 : H2O phase diagram. The results are consistent with the existence of crystalline hydrates at R = 1.33, 3, and 4.5 and identify a mechanistic pathway for hydration. All water is not removed from hydrated ZnCl2 until the system is heated above its melting point. While hydration/dehydration is reversible in concentrated solutions, dehydration from dilute aqueous solutions can result in loss of HCl, the source of hydroxide impurities commonly found in commercial ZnCl2 preparations. The strong interaction between ZnCl2 and water exerts a significant impact on the solvent water such that the system exhibits a deep eutectic at a composition of about R = 7 (87.5 mol %) and a eutectic temperature below -60 °C.}, number={11}, journal={JOURNAL OF PHYSICAL CHEMISTRY B}, publisher={American Chemical Society (ACS)}, author={Pillai, Shelby B. and Wilcox, Robert J. and Hillis, Berkley G. and Losey, Bradley P. and Martin, James D.}, year={2022}, month={Mar}, pages={2265–2278} }
 @article{boyd_ganeshan_tsai_wu_saeed_jiang_balke_duin_augustyn_2021, title={Effects of interlayer confinement and hydration on capacitive charge storage in birnessite}, ISSN={["1476-4660"]}, url={https://doi.org/10.1038/s41563-021-01066-4}, DOI={10.1038/s41563-021-01066-4}, abstractNote={Nanostructured birnessite exhibits high specific capacitance and nearly ideal capacitive behaviour in aqueous electrolytes, rendering it an important electrode material for low-cost, high-power energy storage devices. The mechanism of electrochemical capacitance in birnessite has been described as both Faradaic (involving redox) and non-Faradaic (involving only electrostatic interactions). To clarify the capacitive mechanism, we characterized birnessite's response to applied potential using ex situ X-ray diffraction, electrochemical quartz crystal microbalance, in situ Raman spectroscopy and operando atomic force microscope dilatometry to provide a holistic understanding of its structural, gravimetric and mechanical responses. These observations are supported by atomic-scale simulations using density functional theory for the cation-intercalated structure of birnessite, ReaxFF reactive force field-based molecular dynamics and ReaxFF-based grand canonical Monte Carlo simulations on the dynamics at the birnessite-water-electrolyte interface. We show that capacitive charge storage in birnessite is governed by interlayer cation intercalation. We conclude that the intercalation appears capacitive due to the presence of nanoconfined interlayer structural water, which mediates the interaction between the intercalated cation and the birnessite host and leads to minimal structural changes.}, journal={NATURE MATERIALS}, author={Boyd, Shelby and Ganeshan, Karthik and Tsai, Wan-Yu and Wu, Tao and Saeed, Saeed and Jiang, De-en and Balke, Nina and Duin, Adri C. T. and Augustyn, Veronica}, year={2021}, month={Aug} }
 @article{tsai_wang_boyd_augustyn_balke_2021, title={Probing local electrochemistry via mechanical cyclic voltammetry curves}, volume={81}, ISSN={["2211-3282"]}, DOI={10.1016/j.nanoen.2020.105592}, abstractNote={Understanding the mechanical response of an electrode during electrochemical cycling and its correlation to the device electrochemical performance is crucial to improving the performance of insertion-type energy storage devices, electrochemical actuators, water purification, ion separation and neuromorphic computing applications. In this work, we visualized the electro-chemo-mechanical coupling behaviors during charge storage of anhydrous and hydrated WO3 electrodes via in situ atomic force microscopy (AFM) and developed the concept of mechanical cyclic voltammetry (mCV) curves. The relationship between electrochemical current and strain was investigated with simplified models and the results revealed that the proton insertion/deinsertion process could be described through potential-dependent electro-chemo-mechanical coupling coefficients which might indicate changes in insertion processes during electrode cycling. The mCV mapping results highlight the local heterogeneity and show that the charging processes varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations or chemical compositions with proper electrode designs.}, journal={NANO ENERGY}, author={Tsai, Wan-Yu and Wang, Ruocun and Boyd, Shelby and Augustyn, Veronica and Balke, Nina}, year={2021}, month={Mar} }
 @article{wang_boyd_bonnesen_augustyn_2020, title={Effect of water in a non-aqueous electrolyte on electrochemical Mg2+ insertion into WO3}, volume={477}, ISSN={["1873-2755"]}, DOI={10.1016/j.jpowsour.2020.229015}, abstractNote={Magnesium batteries are promising candidates for beyond lithium-ion batteries, but face several challenges including the need for solid state materials capable of reversible Mg2+ insertion. Of fundamental interest is the need to understand and improve the Mg2+ insertion kinetics of oxide-based cathode materials in non-aqueous electrolytes. The addition of water in non-aqueous electrolytes has been shown to improve the kinetics of Mg2+ insertion, but the mechanism and the effect of water concentration are still under debate. We investigate the systematic addition of water into a non-aqueous Mg electrolyte and its effect on Mg2+ insertion into WO3. We find that the addition of water leads to improvement in the Mg2+ insertion kinetics up to 6[H2O] : [Mg]2+. We utilize electrochemistry coupled to ex situ characterization to systematically explore four potential mechanisms for the electrochemical behavior: water co-insertion, proton (co)insertion, beneficial interphase formation, and water-enhanced surface diffusion. Based on these studies, we find that while proton co-insertion likely occurs, the dominant inserting species is Mg2+, and propose that the kinetic improvement upon water addition is due to enhanced surface diffusion of ions.}, journal={JOURNAL OF POWER SOURCES}, author={Wang, Ruocun and Boyd, Shelby and Bonnesen, Peter V and Augustyn, Veronica}, year={2020}, month={Nov} }
 @article{boyd_geise_toney_augustyn_2020, title={High Power Energy Storage via Electrochemically Expanded and Hydrated Manganese-Rich Oxides}, volume={8}, ISSN={["2296-2646"]}, DOI={10.3389/fchem.2020.00715}, abstractNote={Understanding the materials design features that lead to high power electrochemical energy storage is important for applications from electric vehicles to smart grids. Electrochemical capacitors offer a highly attractive solution for these applications, with energy and power densities between those of batteries and dielectric capacitors. To date, the most common approach to increase the capacitance of electrochemical capacitor materials is to increase their surface area by nanostructuring. However, nanostructured materials have several drawbacks including lower volumetric capacitance. In this work, we present a scalable “top-down” strategy for the synthesis of EC electrode materials by electrochemically expanding micron-scale high temperature-derived layered sodium manganese-rich oxides. We hypothesize that the electrochemical expansion induces two changes to the oxide that result in a promising electrochemical capacitor material: (1) interlayer hydration, which improves the interlayer diffusion kinetics and buffers intercalation-induced structural changes, and (2) particle expansion, which significantly improves electrode integrity and volumetric capacitance. When compared with a commercially available activated carbon for electrochemical capacitors, the expanded materials have higher volumetric capacitance at charge/discharge timescales of up to 40 s. This shows that expanded and hydrated manganese-rich oxide powders are viable candidates for electrochemical capacitor electrodes.}, journal={FRONTIERS IN CHEMISTRY}, author={Boyd, Shelby and Geise, Natalie R. and Toney, Michael F. and Augustyn, Veronica}, year={2020}, month={Aug} }